Hubble Space Telescope photometry of multiple stellar populations in the inner parts of NGC 2419

We present new deep imaging of the central regions of the remote globular cluster NGC 2419, obtained with the F343N and F336W filters of the Wide Field Camera 3 on board the Hubble Space Telescope. The new data are combined with archival imaging to constrain nitrogen and helium abundance variations within the cluster. We find a clearly bimodal distribution of the nitrogen-sensitive F336W–F343N colours of red giants, from which we estimate that about 55% of the giants belong to a population with about normal (field-like) nitrogen abundances (P1), while the remaining 45% belong to a nitrogen-rich population (P2). On average, the P2 stars are more He-rich than the P1 stars, with an estimated mean difference of ΔY ≃ 0.05, but the P2 stars exhibit a significant spread in He content and some may reach ΔY ≃ 0.13. A smaller He spread may also be present for the P1 stars. Additionally, stars with spectroscopically determined low Mg abundances ([Mg/Fe] < 0) are generally associated with P2. We find the P2 stars to be slightly more centrally concentrated in NGC 2419 with a projected half-number radius of about 10% less than for the P1 stars, but the difference is not highly significant (p ≃ 0.05). Using published radial velocities, we find evidence of rotation for the P1 stars, whereas the results are inconclusive for the P2 stars, which are consistent with no rotation as well as the same average rotation found for the P1 stars. Because of the long relaxation time scale of NGC 2419, the radial trends and kinematic properties of the populations are expected to be relatively unaffected by dynamical evolution. Hence, they provide constraints on formation scenarios for multiple populations, which must account not only for the presence of He spreads within sub-populations identified via CNO variations, but also for the relatively modest differences in the spatial distributions and kinematics of the populations.

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Hubble Space Telescope Studies of the Dense Central Regions of Globular Clusters

Symposium - International Astronomical Union ◽

10.1017/s0074180900001340 ◽

1996 ◽

Vol 174 ◽

pp. 19-28

Author(s):

Puragra Guhathakurta ◽

Brian Yanny ◽

Donald P. Schneider ◽

John N. Bahcall

Keyword(s):

Density Profile ◽

Globular Clusters ◽

Hubble Space Telescope ◽

Stellar Populations ◽

Core Collapse ◽

Red Giants ◽

Space Telescope ◽

Blue Straggler ◽

Central Regions ◽

Stellar Density

We present results from an ongoing program to probe the dense central parts of Galactic globular clusters using multicolor Hubble Space Telescope images (WF/PC-I and WFPC2). Our sample includes the dense clusters M15, 47 Tuc, M30, NGC 6624, M3 and M13. The two main goals of our program are to measure the shape of stellar density profile in clusters (the slope of the density cusp in post core collapse clusters, in particular) and to understand the nature of evolved stellar populations in very dense regions and their variation as a function of radius. The latter includes studies of blue straggler stars and of the central depletion of bright red giants. Our recent WFPC2 study of M15 is described in detail.

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Radial variation of the stellar mass functions in the globular clusters M15 and M30: clues of a non-standard IMF?

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2759 ◽

2020 ◽

Vol 499 (2) ◽

pp. 2390-2400

Author(s):

M Cadelano ◽

E Dalessandro ◽

J J Webb ◽

E Vesperini ◽

D Lattanzio ◽

...

Keyword(s):

Globular Clusters ◽

Hubble Space Telescope ◽

Dynamical Evolution ◽

Mass Function ◽

Initial Mass Function ◽

Radial Variation ◽

Wide Field ◽

Data Set ◽

Central Regions ◽

Mass Segregation

ABSTRACT We exploit a combination of high-resolution Hubble Space Telescope and wide-field ESO-VLT observations to study the slope of the global mass function (αG) and its radial variation (α(r)) in the two dense, massive and post core-collapse globular clusters M15 and M30. The available data set samples the clusters’ main sequence down to ∼0.2 M⊙ and the photometric completeness allows the study of the mass function between 0.40 M⊙ and 0.75 M⊙ from the central regions out to their tidal radii. We find that both clusters show a very similar variation in α(r) as a function of clustercentric distance. They both exhibit a very steep variation in α(r) in the central regions, which then attains almost constant values in the outskirts. Such a behaviour can be interpreted as the result of long-term dynamical evolution of the systems driven by mass-segregation and mass-loss processes. We compare these results with a set of direct N-body simulations and find that they are only able to reproduce the observed values of α(r) and αG at dynamical ages (t/trh) significantly larger than those derived from the observed properties of both clusters. We investigate possible physical mechanisms responsible for such a discrepancy and argue that both clusters might be born with a non-standard (flatter/bottom-lighter) initial mass function.

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Wide Field Camera 3 instrument optical design for the Hubble Space Telescope

10.1117/12.550893 ◽

2004 ◽

Cited By ~ 1

Author(s):

Jennifer A. Turner-Valle ◽

Joseph Sullivan ◽

John E. Mentzell ◽

Robert A. Woodruff

Keyword(s):

Hubble Space Telescope ◽

Optical Design ◽

Wide Field ◽

Space Telescope

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Hubble Space Telescope observations of Europa in and out of eclipse

International Journal of Astrobiology ◽

10.1017/s1473550410000285 ◽

2010 ◽

Vol 9 (4) ◽

pp. 265-271 ◽

Cited By ~ 3

Author(s):

W.B. Sparks ◽

M. McGrath ◽

K. Hand ◽

H.C. Ford ◽

P. Geissler ◽

...

Keyword(s):

Hubble Space Telescope ◽

Broad Band ◽

Line Emission ◽

Optical Emission ◽

High Energy ◽

High Energy Particle ◽

Wide Field ◽

Particle Radiation ◽

Space Telescope ◽

Solar Blind

AbstractEuropa is a prime target for astrobiology and has been prioritized as the next target for a National Aeronautics and Space Administration flagship mission. It is important, therefore, that we advance our understanding of Europa, its ocean and physical environment as much as possible. Here, we describe observations of Europa obtained during its orbital eclipse by Jupiter using the Hubble Space Telescope. We obtained Advanced Camera for Surveys Solar Blind Channel far ultraviolet low-resolution spectra that show oxygen line emission both in and out of eclipse. We also used the Wide-Field and Planetary Camera-2 and searched for broad-band optical emission from fluorescence of the surface material, arising from the very high level of incident energetic particle radiation on ices and potentially organic substances. The high-energy particle radiation at the surface of Europa is extremely intense and is responsible for the production of a tenuous oxygen atmosphere and associated FUV line emission. Approximately 50% of the oxygen emission lasts at least a few hours into the eclipse. We discuss the detection limits of the optical emission, which allow us to estimate the fraction of incident energy reradiated at optical wavelengths, through electron-excited emission, Cherenkov radiation in the ice and fluorescent processes.

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Constraints on the spin-pole orientation, jet morphology, and rotation of interstellar comet 2I/Borisov with deep HST imaging

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2192 ◽

2020 ◽

Vol 497 (4) ◽

pp. 4031-4041

Author(s):

Bryce T Bolin ◽

Carey M Lisse

Keyword(s):

Light Curve ◽

Hubble Space Telescope ◽

Wide Field ◽

Deep Imaging ◽

Projected Length ◽

Before And After ◽

Change Position ◽

Time Frames ◽

Pole Orientation ◽

Perihelion Passage

ABSTRACT We present high resolution, deep imaging of interstellar comet 2I/Borisov taken with the Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3) on 2019 December 8 UTC and 2020 January 27 UTC (HST GO 16040, PI: Bolin) before and after its perihelion passage in combination with HST/WFC3 images taken on 2019 October 12 UTC and 2019 November 16 UTC (HST GO/DD 16009, PI: Jewitt) before its outburst and fragmentation of 2020 March, thus observing the comet in a relatively undisrupted state. We locate 1–2 arcsec long (2000–3000 km projected length) jet-like structures near the optocentre of 2I that appear to change position angles from epoch to epoch. With the assumption that the jet is located near the rotational pole supported by its stationary appearance on ∼10–100 h time frames in HST images, we determine that 2I’s pole points near α = 322 ± 10° and δ = 37 ± 10° (λ = 341° and β = 48°) and may be in a simple rotation state. Additionally, we find evidence for possible periodicity in the HST time-series light curve on the time-scale of ∼5.3 h with a small amplitude of ∼0.05 mag implying a lower limit on its b/a ratio of ∼1.5 unlike the large ∼2 mag light curve observed for 1I/‘Oumuamua. However, these small light-curve variations may not be the result of the rotation of 2I’s nucleus due to its dust-dominated light-scattering cross-section. Therefore, uniquely constraining the pre-Solar system encounter, pre-outburst rotation state of 2I may not be possible even with the resolution and sensitivity provided by HST observations.

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